Unloader for compressors



Feb. '28, w33. J, LE VALLEY UNLOADER FOR COMPRESSORS Filed Jan. 2l, 1951 liffall 7. l IML hwwh Il l l l l T WNW INVENTOR.

John/12616129. BY MQ. Mu

HLSATTORNEY.

Patented Feb. 28, 1933 lUNTTED STATES PATENT or-FICE JOHN LE VALLEY, OF PAINTED POST, NEW YORK, A SSIGNOR T0 INGERSOLL-RAND COMPANY, 0F JERSEY CITY, NEW JERSEY, .A CORPORATION 0F NEW JERSEY UNLOADER FOR COMPRESSORS Application led-J'anuary 21, 1931. Serial No. 510,140.

This invention relates to compressors, but

more particularly to an unloader for com-I pressors.

One object of the invention is to minimize the load on the prime mover of the compressor during the starting and stopping periods of the compressor.

Another object is to produce an inexpensive and simplified unloader which may be cheaply maintained and which will be positive in operation.

Other objects will be in part obvious and in part pointed out hereinafter.

In the drawing accompanyingthe speelfication and in which similar reference characters refer to similar parts,

Figure lis an end elevation, partly in section, of a" multiple `cylider compressor and its intercooler having the invention applied thereto, and

Figure 2 is a longitudinal sectional elevation, arranged diagrammatically, of so much of a compressor as will serve to illustrate the invention and a mode of application thereof.

Referring more particularly to the drawing and vat first to Figure l, A designates generally a compessor comprising a base or crank case B upon which are mounted in this instance low and high pressure cylinders C and D respectively. A

The cylinders C and D are provided with heads 'E 'and F respectively having inlet valves G which mav beA of any Well known type for Controlling theadmisson of fluid into the cylinders. The heads E and F are further provided with discharge valves H through which is expelledl the uid compressed in the cylinders.

v In order to reduce the temperature of the medium compressed in the low pressure cylinder C prior to the entry of such air into the high pressure cylinder D the compressor A is provided with an intercooler designated generally by J and comprising a pair of heads K and L connected to the heads E and F respectively, and a series of tubular members O through which the compresseduid flows from the head K tothe head L. The tubular members O are provided exteriorly with fins P to effect rapid radation of heat from 'the compressed medium during its passage compressed, enters the head E through an inlet opening Q into the low pressure cylinder C. After being compressed therein tdP a higher pressure the fluid passes through the intercooler J and through an inlet opening R in the head F into the high pressure cylinder D. Upon being compressed to the required pressure the fluid passes through the discharge valve H and through an outlet opening S in the head F, whence it may iow to a storage receiver (not shown).

Within the cylinders C and D are the working pistons T and U respectively, each having a connecting rod V operatively connected to the crank pin W of a crank shaft X which is illustrated as being conveniently journalled in the crank case B. The connecting rods V are preferably connected to the same crank pin W` so that as one piston approaches the end of its compression stroke the otherpiston will occupy a corresponding position with respect to the end of its suction stroke.

In the operation of compressors of this type, and particularly where the compressor is being driven by a prime mover having a low starting torque, it is desirable that the prime mover be relieved of the heavy load resulting from starting the mechanism against compression. In furtherance of this end the apparatus is provided with relief devices adapted to unload the compressor during speeds of operation which are below the normal operating speed, more specifically, during the starting and stopping periods of the compressor. The meansr'provided for this purpose preferably comprises a conduit Y in the form of a pipe Z which is threadedly connected to a casing secured to the high pressure cylinder D and having a passage c therein to form a continuation of the passage in the pipe Z.

The passage c registers with a passage d in the wall of the cylinder D and said passage (l preferably opens into the compression chamber of the cylinder D at a point closely the pipe Z may, as illustrated, terminate in a plane which coincides with the longitudi-` nal axis of the crank shaft X. To this end of the pipe Z is threaded a plug e which in turn is threaded into the end of a valve cas'- ing I The valve casing f may be supported in any suitable and convenient manner, as for` instance, by a bracket g on the crank case B and is provided with a chamber 7L into which extends a projection of the plug e. The projection j has a bore 1c wherein is disposed a check valve 0, such as a ball, and in the bottom of the bore c is a seat p for thev accommodation ol' the valve 0.

outer ends withv the chamber h. The pas- .Sages 1' are so arranged that they will at all times alord communication between the passage g and the chamber 7L and are therefore in no Wise controlled by thevalve 0.

An opposing seat s is provided for the valve o in the valve casing f and leading from the seat 8 is a passage t which opens into an enlarged bore u also in the valve casing A port o in the valve casing f af- ,30 fords communication between the bore u and the atmosphere.

Disposed in the bore u and a bore 'w in the bracket g coincident with the bore u is a guide sleeve a: wherein is arranged slidably a 5 pin y which abuts with one end the valve o.

Secured to the end of the crank shaft X adjacent the bracket g, as by means of bolts a, is a guide member 2 having a cylindrical recess 3 to slidably receive a hollow plunger C9 4. Within the plunger'4 is arranged a spring 5 to act with one end against the plunger and with the other end against the bot-tom of the recess 8. The spring 5 and the plunger 4 are so arranged that a constant pressure is exerted against the pin y tendlng to maintain said pin 1n contact with the valve 0 during the idle, accelerating and decelerating periods of the compressor A.

To the end that the plunger 4 may be actuated into a position to relieve the valve o of the pressure of the spring 5 a pair of centrifugal weights 6 are mounted on the guide mem er 2 as by means of pivots 7. The weights 6 are provided with hook portions 8 which bear against the outer end of the plunger 4 and thus determine the degree of outward movement of the plunger.

As will be observed, the valve yo is remotely located from the cylinder D so that, in the 'c3 absence of suitable checking devices, the pipe Z would act as a clearance chamber of considerable capacity which would act to lower the eiciency of the compressor. In order therefore to assure maximum output volume C5 of the compressor the casing b is provided casing `The hall valve 12 is reciprocable between the g where-` with a valve chamber 9 having opposed seats 10 and 11 to accommodate a ball valve 12 adapted to control 'communication between the passage c and a passage 13 in the valve and into which the pipe Z opens.

passages 13 and c and leading from the passage 13 to the valve chamber 9 are passages 14 which are located between the ball valve 12 and the pipe Z so that the valve chamber 9 may at all times be in full communication with the pipe Z.

The operation of the device is as follows: The medium to be compressed enters the head E through the inlet opening Q, thence flows through the inlet valve Gr of said head into the cylinder C wherein it is compressed by the piston T and expelled through the discharge valve H into the intercooler J. During the passage of the compressed fluid through the intercooler J the heat resulting from compression is dissipated and the fluid then passes into the cylinder D where it is compressed to a higher value by the piston U and is expelled through the discharge valve H in the head F and through the outlet opening S to its destination.

During this stage of operation, which may be said to be the normal operation, a portion of the fluid compressed in the cylinder D will pass through the passages cl, c, the valve chamber 9, the passages 14 and 13 and through the pipe Z into the passage g where it will act against the ball valve 0. With the compressor operating at a normal speed the weights 6 will be rocked outwardly by centrifugal force and the hooks 8 associated with the weights 6 will then act against the plunger 4 and depress the spring 5 to such a degree that the pin y may be readily displaced by the pressure of theair acting against the ball valve 0 so that the ball valve y0 will seat upon the valve seat 8, thus cutting olf communication between the cylinder D and the atmosphere.

After the ball valve o reaches this closed position pressure fluid will accumulate in the pipe Z until it reaches a value equal to the maximum value of the fluid compressed in the cylinder D'. The pressure fluid thus stored in the pipe Z will then act against the ball valve 12 to maintain said ball valve in the closed position upon its seat 10. In this way only the comparatively short portion of the channel affording communication between the cylinder D and the valve chamber 9 will be exposed to pressure fluid compressed in the cylinder D and the clearance of the cylinder D will therefore be maintained at a minimum, whereas in the 4absence of a suitable checking device, suchas theball valve 12, the entire channelleading from thevcylinder Dto the valve chamber 9 would serve as a clearance pocket.-

Vhile the compressor is operating at normal speed the Weights 6 will render the plunger 4 ineffective to disturb the position ofthe valve o. The valve -0 Will then, as previously stated, occupy its closed position upon the seat s. However, when the compressor is stopped the spring 5 will exert a pressure upon the plunger 4 of sufficient value to overcome the force of the Weights 6 and this movement of the plunger 4 will then be transmitted through the pin y to the valve 0. The valve '0 Will then be actuated toits other limiting position, that is, against the seat p. The pressure fluid previously stored in the passages between the ball valves 12 and 0 will then flow from the valve chamber h through the passages t and o lto the atmosphere, thus providing an outlet directlyto the atmosphere for any pressure fluid which may remain in the intercooler J vand in the cylinder D.

During the subsequent starting period of the compressor the, spring 5 exerts a suflicient pressure against the hooks 8 of the Weights 6 to prevent said Weights from retracting the plunger 4 until the speed of the compressor approaches maximum. The cylinder D will therefore remain in communication with the atmosphere 'so that any air pumped through the` cylinder C and flowing into the cylinder D through the intercooler may find .a ready avenue of escape to the atmosphere. As the speed of the'compressor is accelerated to a` point approaching normal, the weights 6 Will retract or depress the plunger 4 to permit the pressure fluid`flowing through the pipe Z tovagain close the ball valve '0.

I claim: y

1. An unloader for compressors, comprising a conduit into which pressure flows and having a ball relief valve at one end to communicate the conduit with the atmosphere,

said relief valve being held in one limiting position by pressure fluid in the conduit, spring pressed means for actuating the relief val-ve to another limitingA position, centrifugally.Y actuating means for rendering the spring pressed means ineffective to displace y the relief valve during the normal operation contact from the relief -valve during the norend of the conduit and maintained in closed position by pressure fluid entrap ed in the conduit by the valves for controlling the effective capacity o f the conduit.

3. A compressor unloader comprising a conduit communicating at one end with the compression chamber of the compressor and communicating with atmosphere, a check valve inl said conduit normally held closed by pression chamber and speed responsiveA means constructed to hold said check valve open and a second check valve in the conduit relatively close to said compression chamber.

5. A compressor unloader comprising a conduit open to atmosphere and communicating with a chamber in which fluid is compressed, a check valve in said conduit normally held closed by the pressure of fluid Within said chamber to prevent escape of pressure fluid therefrom to atmosphere, and speed responsive means constructed to hold said check valve open when the compressor is at rest.

6. A compressor unloader comprising a conduit open to atmosphere and communicating with a chamber in which fluid is compressed, a check valve in said conduitl normally preventing the escape of pressure fluid from said chamber to atmospheres, speed responsive means constructed yto` hold the check valve open when the compressor is at rest, and a second check valve in the conduit relatively close to said chamber.

7. An unloader for compressors, com rising a conduit into which pressure fluid rom the compressor may flow, said conduit having an outlet toatmosphere, a valve controlling said outlet and normallyactuated by pressure fluid in the conduit to close said outlet, and speed responsive means to actuate said valve to open said outlet when the compressor is at rest and constructed torelease said valve to close upon increase of speed.

'8. An unloader forcompressors, comprising a conduit having an outlet to atmosphere into which pressure fluidfrom the compressor may flow, a valve normally actuated by pressure fluid in the conduit to close said outlet. and speed responsive means to actuate said valve to open said outlet when the compressor is at rest..

In testimony whereof I have signed this JOHN LE VALLEY.

specification. 

